Armor is a little harder - each Armor Type has different abilities, while Armor Material determines the type of defense.
Here's a picture from the forums a few weeks ago that shows all of the armor in the game: armor models, check it out!
R: Boost Ability - Helm - 30s CD
Helms give an ability to boost your stats for ~5 seconds - damage, movement speed, or defense, determined by your Armor Type. These give people a short time for surprise burst, sticking power, or tanking.
D: Role (Utility) Ability - Chest - 30s CD
Chest armor gives you an ability to help you fulfill your typical MMO roles in a fight as a mage, fighter, or tank. Light armor helps you to get more Albion Online Gold, medium armor helps you stick around to deal damage, and heavy armor helps you barge in and disrupt the enemy team. These all have both offensive and defensive uses.
F: Speed Boost - Feet - 20s (or 60s) CD
Boots give you a speed boost, they all have the same icon right now so you won't be able to tell which one people have in a fight.
Armor Passive - All
Light armor gives you better spells (increased damage, healing, or cast speed).
Medium armor gives you better sticking power (increased speed, CC resistance, or better CC).
Heavy armor gives you better defense (increased life, armor, or thorns damage).
Heavy armor has high health, armor, and magic resistance.
Medium armor has a 25% damage/healing boost, medium health/armor/magic resistance.
Light armor has a 50% damage/healing boost, and low health/armor/magic resistance.
Heavy Armor has huge full helms that cover the face, bulky layered chest/legs, and giant shoulder armor.
Medium Armor has open-faced helms, thin/loose chests and sleeves, and small shoulder armor.
Light Armor has scarves, open-faced chest, short sleeves, and no shoulder armor.
Armor Materials - Determined by Chest Material
Plate Armor has ~10% more armor than magic resistance.
Leather Armor has equal armor and magic resistance.
Cloth Armor has ~10% less armor than magic resistance.
Check the size of their shoulders to see what type of chest piece they have, you NEED to know if they are going to be dealing lots of Cheap Albion Online Gold or taking lots of damage, and whether or not they can chase you down. Next most important is their helm - full, half, or scarf? This will determine if they can boost their damage, speed, or sticking power. Boots don't really matter, they have the same abilities and a very small damage or utility boost that will probably match the chest or helm.